The production and shipment of complex and intricate parts mandates the use of packaging giving protection against many environmental hazards such as shock, thermal conditions, moisture and abusive handling. A commonly used means of providing such protection is molded foam cushioning surrounding the article during handling and shipment.
One example of such cushioning is produced by the molding of the foam cushioning directly within a shipping carton. Such carton molding utilizes a mold provided with an image substantially conforming to the shape and size of the article to be packaged and over which is positioned a carton in which the foam cushioning is to be molded. The bottom portion of the mold contains flap mold areas which are designed to receive the lower flaps of the carton and to mold foam panels onto at least two of these carton flaps so as to cover and protect the packaged articles when the carton is closed.
Another example of such foam cushioning is produced by the molding of foam cushions in complementary halves so that the article to be packaged may be protectively encased between the two halves. The benefit of this system is that the foam cushions may be designed so that they can be placed within a similarly sized carton or as integral packages which may be shipped as they are. The molding of these foam cushions utilizes upper and lower male and female molds which determine the shape of the molded foam cushions and the shape and size of the article receiving cavities therein.
To serve as a release agent, a plastic sheet is normally used to cover the surface of the mold prior to the injection of the foam precursors into the carton or into the mold cavity in the case of foam cushion molding. This plastic sheet adheres to the foam and serves to cause the molded foam cushioning to be readily and easily removable from the mold and also as a separation between the article being packaged and the foam cushioning.
For the plastic sheet to serve as an effective release agent while not interfering with the proper molding of the foam cushioning, the plastic sheet must conform closely and smoothly to the surface contours of the mold. On very simple molds, this is easily accomplished by draping the mold with the plastic sheet and applying a vacuum on the surfaces of the mold in order to draw the plastic sheet into conformance with the surface contours thereof. The vacuum may also be used to hold the plastic sheet to the mold during the actual molding operation if such is deemed desirable.
However, because of the complexities of the images on many of the molds used in the molding of foam cushioning, vacuum alone has proven insufficient to cause the plastic sheet to conform closely and smoothly to the surface contours of the mold, but frequently the plastic sheet will have ripples or folds formed therein or the plastic sheet will bridge certain intricate portions of the surface contours resulting in malformed foam cushioning. To ensure that this problem does not occur, it is the usual practice for an operator to manually tuck or place the plastic sheet into those areas of the mold surface where it is anticipated that the vacuum alone will be insufficient to draw the plastic sheet into conformance with the surface contours of the mold prior to the vacuum being drawn on the mold surface.
With the foregoing in mind, it is an object of the present invention to provide an apparatus and method for molding foam cushioning using a plastic sheet as a release agent which overcomes the aforementioned problems of properly positioning the plastic sheet in conformity with the surface contours of complex or intricate molds.
It is a more specific object of the present invention to provide an apparatus and method for molding foam cushioning used in packaging which uses a plastic sheet as a release agent which avoids the necessity of manually placing the plastic sheet in conformity with the surface contours of the mold.